1. Field of the Invention
The present invention is related to a digital video disc player for reproducing DVDs (Digital Versatile Discs) in which video signals, audio signals and sub-picture signals as encoded are written and outputting the digital signals, and to an apparatus for displaying images by receiving the digital signals from the digital video disc player.
2. Prior Art
In the recent years, digital television broadcasting systems and image storing mediums capable of making effective use of storage spaces with compression of the required bandwidth have been realized by making use of the digital compression encoding technique such as MPEG-2.
For example, in the field of the television broadcasting system, satellite transmitted digital television data has already been broadcast while terrestrial transmitted television data has been put in the planning stage. As the image storing medium, DVDs has come onto the market and have been expected as one of the effective image storing media for video products.
The currently available DVD players are provided with analog signal output ports for both images and sounds and sometimes also provided with digital PCM audio output ports. Also, the DVD players are connected to image reproduction systems functioning also as sound reproduction systems, such as televisions, by means of image signal transmission cables and a plurality of the audio signal transmission cables compatible with multiple audio channels.
FIG. 1 is a block diagram showing an exemplary configuration of a DVD player. In the same figure, the DVD player 101 is composed of a spindle motor 105 for turning a digital video disc 103, a pickup head 107, a head amplifier 109 equipped with an equalizer, a decoder/error correction circuit 111, a content scrambling system 113 for copy protecting DVD contents, a program stream demultiplexer (referred simply as the PS demultiplexer hereinbelow) 115, an audio stream decoder 117, a MPEG-2 image stream decoder 119, a sub-picture decoder 121, a navigation manager 123, a presentation engine 125, a menu data generation circuit 127, digital-analog converters 129 and 131 (called simply as D/A converter hereinbelow), a user interface 133 and an access control circuit 135.
Next, the operation of the DVD player 101 will be briefly explained. Laser light is emitted from the pickup head 107 in order to irradiate the digital video disc 103 with a predetermined wavelength. The reflected light is converted to an electric signal which is then output to the head amplifier 109. The head amplifier 109 serves to perform signal amplification, waveform shaping and digitization while the decoder/error correction circuit 111 serves to perform 8-16 decoding and error correction.
Next, the mutual authentication of the digital video disc 103 and the DVD player 101 is performed in order to confirm the authorization. When the authorization is successfully finished, the program stream PS as read from the digital video disc 103 is separated into sounds, videos, sub-pictures, navigation data in the form of packetized elementary streams (PES) by means of the PS demultiplexer 115.
The sound PES is decoded compatible with sound compression encoding technology such as AAC, AC3, MPEG and so forth by means of the audio stream decoder 117 in order to output PCM audio signals.
The video PES is video decoded by means of the MPEG-2 image stream decoder 119. The sub-picture PES is decoded by means of the sub-picture decoder 121. The navigation data PES is received by the navigation manager 123 for use in the reproduction control of the digital video disc 103.
The presentation engine 125 serves to synchronize sounds, videos and sub-pictures as decoded by the decoders 117, 119 and 121 respectively, and output video and sound PCM signals by encoding them in order to be compatible with a television encoding technique such as NTSC, PAL and so forth after overlaying sub-pictures on videos. The D/A converter 129 serves to convert the sounds PCM signals into analog audio signals and output the analog audio signals to an external device. On the other hand, the D/A converter 131 serves to convert the video PCM signals into analog video signals and output the analog video signals to an external device.
The menu data generation circuit 127 serves to generate a menu image and voice guidance for providing and supplying interface to the presentation engine 125 for allowing users to interact with the DVD player. The user interface 133 is provided with a console panel, a wireless controller and so forth in order to transfer user""s operation of the digital video player to the navigation manager 123. The access control circuit 135 serves to select a title to be reproduced, a story of a multiple story title, fast-forwarding, pause, rewinding, and other specific manipulations to be performed.
The currently available the digital TV systems are sometimes provided with analog video input ports and analog audio input ports, but are not provided with a digital video input port.
FIG. 2 is a block diagram showing an exemplary configuration of a prior art digital TV system. In the same figure, the digital TV system 201 is provided with a BS antenna 203, a BS digital tuner 205, a decoder 207, an 8PSK/QPSK error correction circuit 209, a terrestrial antenna 211, a terrestrial digital tuner 213, an FFT error correction circuit 215, a decoder 217, a D/A converter 225, a loudspeaker 227, an NTSC encoder 229, a D/A converter 231 and a CRT 233.
The decoder 217 is provided with a TS processor 219, an audio decoder 221 and an MPEG-2 decoder/video signal processor 223.
Next, the operation of the digital TV system will be explained. Radio wave signals of 12 GHz as received by the BS antenna 203 is converted into intermediate frequencies, decoded and error corrected by means of the decoder 207 and the 8PSK/QPSK error correction circuit 209, and transferred to the decoder 217 in the form of the transport stream.
The VHF-band frequency signal as received by the terrestrial antenna 211 is passed through the terrestrial digital tuner 213 for selecting a channel, decoded and error corrected by means of the FFT error correction circuit 215, and transferred to the decoder 217 in the form of the transport stream.
The decoder 217 serves to select one of the transport streams as transferred from the 8PSK/QPSK error correction circuit 209 and the FFT error correction circuit 215 while sound, video and sub-picture streams are separated from the transport stream as selected by means of the TS processor 219. The audio decoder 221 serves to decode the audio stream into the corresponding PCM audio signals. The PCM audio signals are converted into analog signals by means of the D/A converter 225 and amplified by means of an amplifier (not shown in the figure) in order to output sounds from the loudspeaker 227.
The MPEG-2 decoder/video signal processor 223 serves to video decode the video stream, to sub-picture decode the sub-picture stream and to perform overlay of sub-pictures on the video image. The image signals obtained by overlaying sub-pictures on video images are converted into analog video signals through the NTSC encoder 229 and the D/A converter 231 in order to display moving pictures on the CRT 233.
However, in the case of the digital TV systems of this kind, no digital input port is provided because the specification of the ports for outputting digital images and, in particular, the specification of copyright protection does not have been standardized.
Furthermore, in the recent years, the IEEE-1394 technology has drawn attention of engineers as a multi-purpose digital interface for use in multimedia communications. The IEEE-1394 is a versatile, high-speed, and low-cost serial interface, providing plug-and-play ease of use by automatically configuring necessary control information when connecting peripheral devices with a cable. Furthermore, the IEEE-1394 provides data transfer capability at rates of 100 Mbit/s, 200 Mbit/s, and 400 Mbit/s including the asynchronous packet transfer modes and the isochronous packet transfer mode suitable for real-time data transfer for multimedia applications.
The isochronous packet transfer mode guarantees a fixed transfer speed (bandwidth), which has been assigned in advance for data transfer between two nodes, irrespective of existence of other data transfer channels at the same time. The time division data transfer is performed with the isochronous cycle of 125 xcexcsec in the case of the IEEE-1394 technology. In order to synchronize the cycles of the respective nodes with each other, the clocks of the respective nodes are adjusted to the reference time, called as xe2x80x9cabsolute timexe2x80x9d. Then, the transfer speed is guaranteed by the packet transfer with the packet length proportional to the transfer speed as required of each isochronous transfer channel.
Furthermore, in the case of the IEEE-1394 technology, data is encoded in accordance with the secret (common) key cryptography or the public key cryptography for the purpose of protecting copyright. Namely, copy control information (CCI) is embedded in a digital content in order to indicate the copyright protecting of the digital content, i.e.: xe2x80x9cno more copy allowedxe2x80x9d; xe2x80x9conly one generation allowedxe2x80x9d; xe2x80x9ccompletely inhibitedxe2x80x9d; and xe2x80x9cfreely allowedxe2x80x9d.
When the digital contents, for example, stored in a DVD and so on whose copy is inhibited are transferred, it is confirmed that a predetermined copyright protection system is installed in the device for receiving the digital contents in advance of transferring the digital contents as enciphered. In the case of the standardized specification which has been discussed and adopted in CPT-WG (Copy Protection Technical Working Group), the block to be enciphered is transferred at a maximum speed of 32 Mbits/sec (with 25 MHz system clock).
However, in the case that the prior art DVD player provided with an analog signal output port is connected to a television provided with an analog signal input port, it is troublesome to make correct connection of a number of cables with appropriate ports. Furthermore, the DVD player exchange analog signals with the television system so that the quality of signals tends to be degraded resulting in relatively poor images and sounds.
In order to improve the prior art analog interface, it has been contemplated to make use of a digital interface for connecting a DVD player and a television system. The IEEE-1394 technology, which may be a standard multimedia interface in future, is a promising digital interface also for this use.
Chained lines A to E as illustrated in FIG. 1 are plotted in order to indicate positions in which is provided a possible digital interface between the DVD player and a digital TV system when the analog outputting DVD player is provided with a digital output port. The chained line F is plotted in order to indicate positions in which is provided the analog interface between the DVD player and the digital TV system.
However, there are following shortcomings in the digital interfaces indicated by the chained lines A to E as illustrated in FIG. 1. In this case, it is assumed that the digital interface is implemented by means of the IEEE-1394 technology.
In the case that the digital interface is implemented on either of the chained lines A, B and C, substantial additional implementation of hardware and software is required for the television system in the same manner as required for the conventional DVD player.
Namely, the television system has to be provided with decoders for sounds, videos and sub-pictures. In other words, part of a DVD player has to be implemented within the television system. Particularly, it is a heavy burden for the television system, from the view point of the circuit scale as available, to provide audio decoders for all the sound compression encoding technologies such as AAC, AC3, MPEG and so forth.
Software processing for implementing the navigation function for the sub-pictures is a most complicated and difficult treatment as conducted in the DVD player and, therefore makes the burden placed upon software too heavy for a television system.
In the case that the digital interface is implemented on the chained line D, it is expedient that the television system need not audio decode and treat the navigation functions. However, also in this case, there is a shortcoming that sounds, videos and sub-pictures have to be processed in synchronism with each other.
In the case that the digital interface is implemented on the chained line E, there are following shortcomings. Namely, since the PCM video signal requires a wide band of 166 Mbit/sec which exceeds 32 Mbit/sec, i.e., the maximum band width of the ciphering ability of the IEEE-1394 technology, six equivalent cipher circuit have to be provided. This is not practicable so that it is difficult to copy protection from illegal copies.
The present invention has been made in order to solve the shortcomings as described above. It is an important object of the present invention to provide a digital video disc player and an apparatus for displaying images in which it is possible to establish the synchronization among the video signals, the audio signals, the sub-picture signals as transferred through the digital interface from the digital video disc player to the apparatus for displaying images.
It is another associated object of the present invention to provide a semiconductor device provided with a digital video disc player and an apparatus for displaying images in which it is possible to reduce the transmission band width of the digital interface between a digital video disc player and an apparatus for displaying images, and making it possible to effectively protect the copyright of digital contents without increasing the ciphering circuit suitable for the IEEE-1394 technology.
It is further associated object of the present invention to provide a semiconductor device provided with a digital video disc player and an apparatus for displaying images in which the navigation function is implemented only in the digital video disc player while the common MPEG2 image decoder is utilized in the apparatus for displaying images of both the video signals which are broadcasted or the video signals which are transmitted through the digital interface from a digital video disc player together with the audio signal and the sub-picture signals, so that a little burden is placed on software for make use of the digital interface.
It is further associated object of the present invention to provide a semiconductor device provided with a digital video disc player and an apparatus for displaying images in which the circuitry of the apparatus for displaying images of MPEG-2 is recognized as designed to support the IEC61883 standard for transmitting and receiving MPEG2 transport streams on a 1394 network.
In brief, the above and other objects and advantages of the present invention are provided by a new and improved semiconductor device provided with a digital video disc player for reading audio signals, video signals and sub-picture signals as compressed, encoded and multiplexed from a digital video disc, and outputting digital signals in accordance with a transmission format, comprising:
a reference time counter for counting a reference time on the basis of which the video signals, the audio signals and the sub-picture signals are synchronized with each other; and
a digital interface for outputting the video signals, the audio signals and the sub-picture signals in the form of the digital signals together with time information indicative of the reference time.
In accordance with another aspect of the present invention, a semiconductor device provided with an apparatus for displaying images comprising:
a digital interface for receiving video signals, audio signals and sub-picture signals in the form of digital signals together with time information indicative of a reference time;
a reference time counter for receiving the time information and counting the reference time on the basis of which the video signals, the audio signals and the sub-picture signals are presented in synchronization with each other; and
a presentation circuit for presenting the video signals, the audio signals and the sub-picture signals in synchronization with each other on the basis of the reference time as counted by the reference time counter.
In accordance with a further aspect of the present invention, a semiconductor device provided with a digital video disc player for reading audio signals, video signals and sub-picture signals as compressed and encoded in accordance with the MPEG-2 technique from a digital video disc, and outputting digital signals in accordance with a transmission format, comprising:
an STC counter for counting a reference time on the basis of which the video signals, the audio signals and the sub-picture signals are synchronized with each other for presentation;
means for outputting the MPEG2-PES of the video signals as read from the digital video disc in the form of isochronous packets as compliance with a digital interface together with the reference time;
a sub-picture decoder for decoding the sub-picture signals to generate on-screen data; and
means for outputting the on-screen data in the form of isochronous packets as compliance with the digital interface in synchronism with the reference time.
Also, in accordance with a preferred embodiment of the present invention, the digital video disc player further comprises means for outputting the MPEG2-PES of the audio signals in the form of isochronous packets as compliance with the digital interface in synchronism with the reference time.
Furthermore, in accordance with a preferred embodiment of the present invention, the digital video disc player further comprises an audio decoder for generating the PCM audio signals of the audio signal as read; and means for outputting the PCM audio signals in the form of isochronous packets.
Furthermore, in accordance with a further preferred embodiment of the present invention, the MPEG2-PES is outputted as the isochronous packets with padding by the means for outputting the MPEG2-PES of the video signals as read in the form of isochronous packets.
Furthermore, in accordance with a further preferred embodiment of the present invention, the MPEG2-PES is converted into transport streams and outputted as the isochronous packets by the means for outputting the MPEG2-PES of the video signals as read in the form of isochronous packets as compliance with the digital interface together with the reference time.
Furthermore, in accordance with a further preferred embodiment of the present invention, when starting reproduction, the system clock reference contained in the program stream is detected packetized and outputted in accordance with a transmission format as compliance with the digital interface by the means for outputting the MPEG2-PES of the video signals as read in the form of isochronous packets as compliance with the digital interface together with the reference time.
In accordance with a further aspect of the present invention, a digital video disc player for reading audio signals, video signals and sub-picture signals as compressed and encoded in accordance with the MPEG-2 standard from a digital video disc, and outputting digital signals in accordance with a transmission format, comprising:
an STC counter for counting a reference time on the basis of which the video signals, the audio signals and the sub-picture signals are synchronized with each other;
a sub-picture decoder for decoding the sub-picture signals and generating on-screen data as synchronized with the video signals;
an audio decoder for generating PCM audio signals from the audio signal as read;
packetizing the MPEG2-PES of the audio signal as read, the PCM audio signals and the on-screen data in combination in accordance with a transmission format as compliance with the digital interface and outputting packets whose size is equivalent to that of the MPEG2-TS.
Furthermore, in accordance with a further preferred embodiment of the present invention, the MPEG2-PES is packetized as compliance with the digital interface while the system clock reference value is inserted in the isochronous header by the means for outputting the MPEG2-PES of the video signals as read in the form of isochronous packets as compliance with the digital interface.
In accordance with further aspect of the present invention, a digital video disc player for reading video signals as compressed and encoded from a digital video disc, and outputting digital signals in accordance with a transmission format, wherein a discontinuity flag is inserted into an isochronous packet as compliance with the digital interface to indicate discontinuity of a transfer stream when discontinuous reproduction operation is performed during a seamless moving image is reproduced.
In accordance with a further aspect of the present invention, an apparatus for displaying images comprising:
a digital interface for receiving video signals, audio signals and sub-picture signals in the form of digital signals together with a reference time to be loaded onto an STC counter;
a STC counter for counting the reference time on the basis of which the video signals, the audio signals and the sub-picture signals are presented in synchronization with each other; and
means for loading the reference time as received onto the STC counter;
an MPEG-2 image decoder for decoding the video signals as received;
an presentation engine for synchronizing the video signals as decoded with reference to the STC counter;
means for overlaying the sub-picture signal on the video signals in synchronism with each other;
means for digital-to-analog converting the overlaid signals and displaying digital-to-analog converted signals; and
means for outputting sounds on the basis of the audio signal as received.